Logs (also referred to as lumber) received at a typical wood processing facility, such as a sawmill, vary both in diameter and length. The logs may be tapered differently from one another and come in a variety of physical shapes, all of which are different from the ideal log shape, which is straight, has a perfectly circular cross-sectional area and a constant diameter throughout its length. The logs are typically deep piled on an in-feed log deck, such that the logs become skewed, crossed and/or tangled. It is generally necessary to feed the logs to the processing facility one log at a time. It is also desirable that there be no interruption in the flow of logs into the wood processing facility.
A log singulator is used to separate logs from a pile of logs on an in-feed deck and feed them one at a time to an out-feed conveyor. Published U.S. Patent Appl'n Ser. No. 2002/0158078 discloses an example of a prior art log singulator, the entire contents of which is incorporated herein by reference. The singulators come in many different types.
“Step sorter” singulators, such as the devices shown by U.S. Pat. No. 5,423,417 (“Log Ladder”), U.S. Pat. No. 5,257,688 (“Step Feeder”) and U.S. Pat. No. 5,174,351 (additions to “Step Feeder”), sort logs in a series of steps which are distributed horizontally along a small vertical incline. The main disadvantages of such singulators are imprecise separation of logs (i.e. tendency to carry more than one log at a time toward the wood processing facility) and high floor area occupied within the processing facility. Another common disadvantage of some of these singulators is the absence of surge and catch-up features. Such features are usually used to ensure that logs are fed at an optimal rate to a wood processing facility.
“Rotary sorter” singulators, such as the device described in U.S. Pat. No. 5,011,024 (“Rotary Log Sorter”), have drums with pockets or arms that rotate continuously. The pockets or arms carry logs one at a time to an out-feed conveyor. A main problem with such singulators is that occasionally more than one log will be taken in by the pockets or arms. Such singulators are also poor at efficiently raising logs vertically, as they occupy more floor space than desired when doing so. Another problem associated with such singulators is the inability to singulate oddly-shaped logs. A further common disadvantage of such singulators is the absence of surge and catch-up features to ensure that logs are fed at an optimal rate to a wood processing facility.
“Oscillating quadrant/arc” singulators, such as the device described in U.S. Pat. No. 5,119,930 (“Quadrant Log Feeder”), elevate logs along a curved surface. The main disadvantages of such singulators are imprecise separation of logs and low singulation speed (i.e. the number of logs per minute that can be separated from an in-feed log deck and fed, one at a time, to an out-feed conveyor). Also, such singulators do not provide for optimal surge and catch-up features to ensure that logs are fed, one at a time and at an optimal rate, to an out-feed conveyor.
Weyerhaeuser Company designed and built the first clockwork style reciprocating log singulator and named it “The Clockwork Feeder.” Weyerhaeuser built a few of the Clockwork feeders, which was suitable for short wood of 8 to 20 feet in length, for a few Weyerhaeuser (Weyco) lumber mills on the west coast. To our knowledge, no patent was obtained.
In 2004, PSI Sales designed and built their version of the Clockwork Feeder for Weyco Dierks, which is shown in FIGS. 1A-1C. Due to the shallow design of the Weyco Clockwork feeder, the Dierk's machine required an additional rotary style pre-feeder to help breakdown the deep pile of incoming logs. One major disadvantage with the Clockwork feeder(s) is it's a shallow machine that actually loses elevation from the in-feed deck to the out-feed conveyor. Due to this design limitation the clockwork feeder can only be fed with a single layer of logs coming to it or it has to be supplemented with an additional pre-breakdown machine device. One of the Clockworks assets is, due to its balanced design, the feeder can be cycled at high rates and requires low horsepower requirements.
In 2005, a modified version of the Weyco Clockwork Feeder was made, as shown in FIG. 2. One of the key advantages of this design feeder was the ability to gain elevation from the in-feed deck to the Outfeed conveyor, which helps to handle a deep pile of incoming logs. However, the largest problem with the feeder is, due to its unbalanced design, it has a slower cycle time and requires much more horsepower to run.
In 2008, we built a “high-lift” clockwork style singulator for Wood Lumber in Idabel, Okla., as shown in FIG. 3.
In 2009-2010, we built a singulator for Dixon Lumber in Eufaula, Ala., which is based off of the original clockwork feeder. See FIG. 4.
There is a need to improve the input log capability and efficiency of the prior art singulators.